Sin^4a+sin^2a*cos^2a+cos^2a=1

[latex]sin^4\alpha+sin^2\alpha*cos^2\alpha+cos^2\alpha=1 \\sin^2\alpha(sin^2\alpha+cos^2\alpha)+cos^2\alpha=1 \\sin^2\alpha+cos^2\alpha=1 \\1=1 \\OTBET:\alpha\in R[/latex]